1. Field of the Invention
The present invention generally relates to motor drives in computer systems and, more particularly, to motor drives in battery powered computer systems.
2. Description of the Related Art
Battery powered computer systems, that is, computer systems that can be wholly empowered by a battery or batteries, are well known in the art of computer systems. One of the major advantages of battery powered computer systems is the fact that a user is able to operate such a system without having to be in the immediate vicinity of or to otherwise depend upon conventional stationary power sources such as 110 volt wall sockets. Thus, battery powered computer systems may be operated at many more locations than systems that must be connected to a stationary power source to operate. A second advantage of battery powered systems is that fact that they are generally made small and light, so as to be easily transportable. "Notebook sized" computers weighing about 31/2 pounds, which can easily fit into a briefcase for travel, are presently not uncommon. Examples of battery powered computer systems include but are not limited to many laptop, notebook, pen-based, and sub-notebook systems.
A disadvantage of battery powered computer systems is the limited runtime of those systems. Runtime is defined as the amount of time for which the battery powered computer system can operate on its battery source (i.e., its battery or batteries) without replacing or recharging that source. There are two primary factors in determining runtime: battery capacity and power consumption rate. Battery capacity, or the amount of power that can be delivered by the battery source, generally relates to battery size among similar or identical types of batteries. Battery size among similar or identical types of batteries, in turn, generally relates to battery weight. Power consumption rate depends on the amount of power consumed by a given system, and the speed at which the given system consumes that power. Generally, the runtime of a battery powered computer system increases with an increase in battery capacity and/or with a decrease in power consumption rate.
Ideally, those skilled in the art would like to increase system portability (by reducing system size and weight) while increasing system runtime. Unfortunately, as may be gathered from the discussion above, attempting to increase system runtime by increasing battery capacity generally causes an increase in the size and weight of the system's battery source, which reduces portability. Thus, toward the goal of increasing battery powered computer system runtime, those skilled in the art have come to focus upon reducing the power consumption rate of battery powered computer systems. Ideally, decreases in power consumption rate can ultimately allow decreases in battery capacity (i.e., battery size and weight) with runtime still being acceptable.
One method of reducing the power consumption of a system is to reduce the power consumption of a component of that system. A component that consumes power within many battery powered computer systems is a drive motor. Battery powered computer systems typically contain drive motors to cause rotation for operation of media devices, such as hard disk drives and floppy disk drives. In a typical prior art battery powered computer system, a drive motor receives power from a motor controller, the motor controller receives power from a DC to DC converter, and the DC to DC converter receives power from a system power source. The system power source is usually the computer system's battery; however, power can be obtained from a temporary hook-up to a stationary power source such as a 110 volt wall socket that has been rectified into a DC power source. The DC to DC converter is typically a linear or switching regulator taking the power source and converting it to a preset DC voltage for use in the entire computer system. The motor controller typically contains a linear regulator further converting the DC to DC converted voltage into a voltage for use by the drive motor and for internal control circuitry for operating the drive motor.
To reduce the power consumption rate of drive motors, those skilled in the art have heretofore enabled motor controllers (via power management firmware) to shut down the drive motor after predetermined periods of inactivity. Such systems are equipped with a timing mechanism to track length of periods of time during which the drive is not used, and such systems are further equipped with structure for starting and stopping the drive motor. Once a drive is in a shut down state, a renewed need for use of the drive causes the system to restart or reactivate the drive motor. Once the drive is given a command to activate the motor, there is a delay in time until the drive motor reaches its operating speed. This delay is called the spin-up time delay. Although spin-up time delay is considered undesirable primarily, because the driven structure (e.g., hard disk) is unusable until driven at its operating speed!, the increased runtime obtained by reduced power consumption provided by shutting down the drive motor is usually considered to outweigh the undesirability of the delay. Still, minimizing the amount of spin-up time delay is an important, desired goal in the art.
Spin-up time delay is in part determined by the electrical potential supplied to the motor controller and the drive motor. The greater the amount of electric potential applied to the drive motor, the faster it "spins up". Existing battery powered computer systems supply voltage to the drive motor indirectly and to the motor controller directly from a DC to DC converter. A typical DC to DC converter supplies only 5 volts to the drive motor and the drive motor controller. It is a shortcoming and deficiency of the prior art that there is not an easy way to apply a greater amount of electrical potential than 5 volts to the drive motor.
Another disadvantage of the current methods for powering drive motors is power loss in the DC to DC converter. As previously explained, the DC to DC converter takes voltage from a source such as the system battery and changes the voltage from that source into a voltage for use by the computer system. The typical efficiency for existing DC to DC converters is about 90%. This means that about 10% of the energy taken from the power source is lost, principally as heat. It is a shortcoming and deficiency of the prior art that current methods for powering drive motors have this power loss.
A further disadvantage of the current methods for powering a drive motor is power loss in the motor controller. In addition to controls for the motor, the motor controller contains a linear regulator for converting the DC voltage from the DC to DC converter into a voltage for use by the motor. For example, the linear regulator within the motor controller may receive a voltage (such as 5 volts) from the DC to DC converter (drawing 1 amp) and convert that voltage into a voltage (such as 3 volts) for use in the drive motor. In this example, two watts of power are lost in the linear regulator (generally as heat). It is a shortcoming and deficiency of the prior art that current methods for powering drive motors have this power loss.
Based upon the foregoing, it should be appreciated that there are a number of significant shortcomings and deficiencies in the art that have heretofore contributed to spin-up time delays incurred in the interest of increasing system runtime. These shortcomings and deficiencies include no provisions for applying higher voltages to drive motors, no provisions for eliminating power losses in the DC to DC converter in the source-converter-controller chain that empowers the drive motor, and no provisions for eliminating power losses in the motor controller in the source-converter-controller chain that empowers the drive motor.